1. Field of the Invention
The present invention relates to press grain drills, and more particularly to arrangements in which each of a plurality of opener units has a shovel for digging a furrow of desired depth and depositing seed therein and a following press wheel for compacting soil over the seeds at a selected depth.
2. History of the Prior Art
Grain drills form a well-known and useful part of available farm machinery. Such units typically employ a plurality of shovels generally equally spaced along the length of the unit for digging a plurality of parallel furrows in the ground as the unit is towed over the ground. The shovels are coupled such as by hoses to receive a continuous supply of seeds. The seeds are deposited in the soil by the shovels as the furrows are dug. The grain drill may be towed as a single unit or as a plurality of interconnected units by an appropriate vehicle such as a tractor. An example of a grain drill is provided by U.S. Pat. No. 3,628,611 of Carlson, issued Dec. 21, 1971.
It is common practice in grain drills to provide each shovel with a following press wheel. Each press wheel follows the associated shovel in the furrow created by the shovel and runs at a depth which is normally less than that of the shovel because of soil returning or flowing back into the furrow ahead of the press wheel. An example of a grain drill utilizing press wheels is provided by U.S. Pat. No. 3,402,938, McCallum, issued Sept. 24, 1968.
Presently known grain drills suffer from a number of limitations. One such problem relates to the need for a relatively heavy object such as a seed box mounted on the drill to provide for penetration of the shovels in the ground. The presence of the heavy and cumbersome seed box makes it difficult to design drills which can be easily folded or otherwise rearranged for ease of transport and maneuvering. Another problem stems from the fact that the drills are incapable of maintaining substantially constant shovel and press wheel depths as the level of seed in the seed box varies and as soil or terrain irregularities occur. As the seed level in the seed box decreases and the weight of the box decreases, shovel penetration decreases. Frequently the shovels are spring loaded in a vertical direction for maintaining penetration in the ground. Factors such as variations in the terrain vary the spring tension and thereby the downward force and the penetration of the shovel. Consequently, compactness of soil around the seeds varies considerably. It is known that the latter is extremely important with respect to the proper germination of the seed, it being understood that a proper and uniform compactness would be desirable if at all possible.
Still further problems may reside in the design of the supporting wheeled framework for the drill unit and the manner in which the shovels and associated press wheels are raised to provide clearance during towing to and from the job and are lowered into the operative positions while on the job.
Accordingly, it is an object of the present invention to provide an improved press grain drill.
A more specific object of the invention is to provide a press grain drill in which individual opener units include a shovel which is self-penetrating and a press wheel which undergoes vertical movement at a rate greater than that of the shovel for changes in the position of the drill so as to maintain the shovel and press wheel at substantially constant depths within the ground.
Still further objects in accordance with the invention are to provide a press grain drill which exerts a substantially constant downward force on the press wheel and shovel independent of the positions of the shovel and press wheel to provide for uniform soil compaction despite terrain irregularities and the like.
It is a still further object of the present invention to provide a press grain drill in which the individual opener units may be conveniently raised for towing and lowered into the operative position for plowing, seeding and compacting.